1. Field of the Invention
This invention relates to a highly active catalyst for producing polyolefins having a good particle diameter distribution and to a polymerization process employing such a catalyst.
2. Description of the Prior Art
There have been developed and proposed many catalyst systems for low-pressure processes of producing polyolefins which comprise a transition metal compound of a metal of Groups IV to VI A of the periodic Table and an organometallic compound of a metal of Groups I to III of the Periodic Table since the Dr. Ziegler's discovery. Most of the catalyst systems, however, are not sufficient with the catalyst activity and require the step of removing catalyst residue from the polymer formed and accordingly, the cost of producing polymers are high. Recently, development of highly active catalysts capable of eliminating the step of removing catalyst residue from the polymer formed and simplifying the process to reduce the cost of producing polymers is extensively carried out and there has been proposed a group of catalysts employing the reaction products of inorganic magnesium compounds or organomagnesium compounds and titanium compounds or vanadium compounds.
It would be highly desired that the catalyst activity per transition metal atom in the catalyst is increased and at the same time all the characteristic features required for industrial catalysts, such as the particle diameter distribution of polymers, the bulk density of polymers and the stability of catalysts, are improved. At the present, a further increase in the catalyst activity in order to eliminate the catalyst residue removal step and at the same time a stable operation of slurry polymerization process continuously for a long period of time, and an improvement on the particle performances such as unification of the particle diameter of the polymer formed and increase in the bulk density of the polymer formed are considered very important from the industrial view point.
As one means for preparing catalysts having a high catalyst activity per transition metal atom, it is known to employ a solid catalyst component obtained by reacting a solid inorganic oxide with a transition metal. Japanese Patent Application (OPI) No. 2258/1971 describes a process for polymerizing olefins by employing a solid catalyst component obtained by firstly reacting silica with an alkylmagnesium halide and secondly reacting the resulting reaction product with a titanium compound. Japanese Patent Application (OPI) No. 92879/1975 describes a method of preparing a carrier catalyst by heating silica and a magnesium halide and adding a transition metal compound thereto. Further, Japanese Patent Application (OPI) No. 47990/1976 describes a method of preparing a solid catalyst component by firstly reacting a silicon compound synthesized by the high temperature process with an organomagnesium compound and secondly reacting the resulting reaction product with a titanium compound. Furthermore, Japanese Patent Application (OPI) No. 95790/1977 describes a method of obtaining a solid catalyst component by firstly contacting silica with an alcohol-soluble magnesium compound and a solution of a titanium halide and secondly vaporizing the alcohol to concentrate the reaction mixture solution. Still further, Japanese Patent Application (OPI) No. 148093/1979 describes a method of preparing a catalyst by dissolving a titanium compound and a magnesium compound in an electron donor and impregnating a porous carrier in the resulting solution. Also, Japanese Patent Application (OPI) No. 115405/1980 describes a method of preparing a catalyst comprising a solid inorganic oxide, an organomagnesium compound, a Lewis base compound and titanium tetrachloride.
According to these catalysts, the catalyst activity per transition metal atom is considerably high but the catalyst activity per unit weight of the solid catalyst component is not satisfactory. Thus, further improvements on the catalyst productivity of polymers and at the same time on the particle diameter distribution and the bulk density of the polymers formed are demanded.
As a result of the study on solid inorganic oxides, various organomagnesium compounds and various reagents in order to improve the above-described points, it has now been discovered that the solid substance obtained by reacting an inorganic oxide carrier substance, an inert hydrocarbon-soluble organomagnesium and a chlorosilane compound having a Si-H bond, separating and washing the reaction product with an inert hydrocarbon and reacting the reaction product with a transition metal compound, in combination with an organometallic compound, is a highly active catalyst for producing polyolefins having a good particle diameter.